Hydraulic lash adjuster



June 22, 1954 w. J. PURcHAs, JR., ET Al. 2,681,644

HYDRAULIC LAsH AnJusTER Filed Jan. 5, 1950 I Gttornegs Patented June 22, 1954 UNITED STATES ATNT OFFICE HYDRAULIC LASH ADJUSTER Delaware Application January 5, 1950, Serial No. 136,906

(Cl. 12S-90) Claims.

This invention relates to internal combustion engines and the like and particularly to valve operating mechanisms therefor of the automatic lash take-up type.

One of the objects of the invention is to provide an improved hydraulic lash adjuster for use in such mechanisms requiring a minimum number of component parts each of simple design and low manufacturing cost.

Another object of the invention is to provide such a lash adjuster designed to be supplied during operation with hydraulic fluid in the form of oil under pressure from the engine lubricating system, novel means being incorporated in the lash adjuster structure for venting the same of entrained air in the engine oil supplied thereto.

Another object of the invention is to provide an improved valve operating mechanism including a hydraulic lash adjuster wherein the aforesaid venting is accomplished by an axial passage through one thrust transmitting end thereof, and a member in thrust receiving relation with said lash adjuster end having means for conducting such vented air to the outside atmosphere.

The means by which these and other objects of my invention are attained will be readily apparent from the following description, having reference to the drawing, wherein:

Figure 1 is a sectional elevational view of a portion of an internal `combustion engine incorporating a valve operating mechanism in accordance with my invention.

Figure 2 is an enlarged fragmentary View similar to Figure 1 showing the details of the hydraulic lash adjuster and the lower end of the push rod.

Figure 3 is a further enlarged detail sectional View taken substantially on line 3-3 of Figure 2.

Figure 4 is an enlarged perspective view of the lower end of the push rod.

Referring to the drawing there is shown a hydraulic lash adjuster designated generally by the numeral I which is rotatably and slidably supported in a bore 2 provided therefor in the engine cylinder casing or frame 3. Opposite ends of the lash adjuster respectively abut the lower end face 5 of the push rod 6 and the working surface of the cam 4, which cam is offset longitudinally of its shaft I3 from the axis of the bore 2. The upper end of the push rod, in turn, engages one arm of the valve rocker 8 whose other end engages the upper end of the engine valve 9 which is slidably supported for reciprocable movement in a bushing lll secured in the engine cylinder head I I, there being a spring I2 biasing the valve 9 to closed position as shown. Rotation of the cam shaft I3 during engine operation causes the cam thereon to both rotate and reciprocate the lash adjuster I, reciprocably carrying with it the engine push rod 6 and oscillating the rocker Si to effect opening and closing of the valve 9. Providing the lash adjuster I is of proper length, the valve spring I2 will serve to return it to the hase circle of the cam 4 after each valve lift; and no clearance (lash) will exist between the cam and the valve while the latter is in closed position, thereby preventing noise and wear due to hammering of the parts, all in a manner well understood in the art.

As best seen in Figure 2 our lash adjuster I comprises a member having the general shape of an upright cup shaped cylinder I, the end wall I5 of which rests directly on the cam 4. The external cylindrical periphery I6 of the cylinder i4 is provided with an annular groove I1 intermediate the ends of the cylinder I4, which groove is in registry with an oil passage or gallery i8 leading from the engine oil pressure lubricating system (not shown) through the engine cylinder casing 3. Extending through the wall or the cylinder I4, at the upper end of the annular groove Il, is a port I9 by means of which the oil for supplying the lash adjuster is conducted to the cylindrical bore 2li of the cylinder I4. This bore 20 is of uniform diameter for a considera-ble distance above and below the port I9 and terminates at its upper end in an enlargement 2i adjacent the upper end of the cylinder i4, which enlargement is provided with an annular groove 22. The lower end of the bore 2D terminates in an enlargement 23 which in turn terminates at its lower end in a well 24 of smaller diameter than the bore 2U, the lower end of which well has a further reduced portion 25. The reduction in diameter between the enlargement 23 and the well 24 provides a shoulder 26 which in the event the engine is stopped with the valve 9 not fully closed will limit the downward travel of the part now to be described.

In nesting relation within and slidably supported by the cylinder bore 2G is a second member in the form of a cup shaped piston 2l having an end wall 28 from which centrally depends a reduced diameter portion 30. A central aperture 29 extends through the end wall 28 and portion 30. Loosely surrounding the portion 30 is a generally conical-shaped inverted cup or cage member 3l having an external flange t2 at its upper end which is held. against the end wall 28 by a compression coil spring 33 whose lower end seats on the end wall i of the cylinder within the reduced portion of the weil 2t. The end wall 313 of this cage member serves to loosely retain the ball 35 in position for closing the lower end of the aperture 29 and has a number of openings 36 extending therethrough.

The internal surface of the piston comprises a series of aligned connecting bores 42, 43 and d4 the diameters of which are arranged in. stepped decreasing relation from the upper end of the piston downwardly. An annular groove et is provided around the external periphery ci the piston for communication with the cylinder port i9, and a port 4l extending radially through the side wall of the piston connects this groove lit with the intermediate bore 43 of the piston. The aperture 29 through the end wall 28 and reduced portion of the piston communicates at its up per end with the lowermost piston bore rfid.

Closing the upper end of the piston is a plug 45 which nts Ythe uppermost bore i2 and an outwardly flanged rim it abutting the upper end face il of the piston. This plug i5 is centrally recessed at its upper end to form a spherically concave seat 45 for the lower end face 5 of the push rod S, and extending centrally through the plug between the seat d8 and its lower end is an air vent passage 59.

The lower end face 5 of the push rod as best shown in Figure 4 is convex in shape to conform with the spherical seat #i3 of the plug and has a centrally disposed depression 50 which is of larger diameter than the passage 49 and in direct communication. therewith. The push rod end face 5 is further provided with one or more (two being shown) grooves 5I which lead outwardly generally from depression 50 to the lateral extremities of end face 5.

Retained by the annular' groove 22 provided in the uppermost bore 2| of the cylinder ill is outwardly expansible snap ring 52. This ring is preferably non-circular in shape, having side portions 53 and 54 which serve as abutments for the plug l5 to prevent complete withdrawal of the piston 2'! from the cylinder I4 under the force of the spring 33 during installation and removal of the lashv adjuster assembly from the engine.

In operation, a body of oil completely iills the space between the piston 21 and the lower end of the cylinder l at all times and serves to transmit thrust between these members during each valve lifting stroke of the cam li. By rea son of the cam t being oiiset longitudinally of the axis of its shaft i3 with respect to the axis of the cylinder i4, this cylinder rotates continuously in one direction since' its end wall i5 remains in constant surface engagement with the cam. The relatively close t of the piston in the cylinder causes the piston to rotate in the same direction, though generally at a somewhat lower rate because of the frictional drag effected thereon by the push rod 6. During each lifting stroke the ball check valve closes the lower end of the passage 29 preventing the escape of oil therethrough to the interior of tne piston. Some oil, however, will leak between the piston and cylinder to the annular groove lll from which it iiows into the piston through the port M. A limited amount of such leakage is necessary in order that the lash adjuster will shorten somewhat with each lifting stroke and thereby accommodate any elongation of the push rod E or valve stem i@ due to increased operating temperatures.

Following each lifting stroke and return of the valve 9 to its closed position, the lashradjuster spring 33 operates to elongate the lash adjuster by moving the piston 2'! outwardly of the cylinder i4 the necessary amount to maintain the cylinder I4 in contact withV the cam i and the piston 21 in solid abutting relation (through theplug 45, push rod E5 and rocker 8) with the upper end of the engine valve 9. This elongation of the lash adjuster and consequent enlargement of the space between the piston and cylinder causes the ball 35 to leave its seat on the reduced diameter portion 3i) of the piston and oil to flow through the passage 29 from the interior of the piston in sufiicient quantity to maintain the space below the piston completely iilled.

The interior of the piston I4 thus serves as a reservoir for supplying theY space below the piston, and Vthis reservoir is maintained substantially filled by delivery of oil thereto under pressure from the engine lubricating system through the gallery I8, annular groove ii and ports l and 4l. Since the oil flowing into the piston from the engine lubricating system generally contains a substantial amount of entrained air it is desirable that means be provided for venting the piston in order that this air is not carried downward with the oil through the passage 29 to the space below the piston. In accordance with our invention, this air and the engine oil delivered in excess of that required to maintain the reservoir lled is permitted to pass out of the piston through the aperture 5:9 in the plug 45 to the depression 58 in the push rod end face 5 and thence along the grooves 5l to atmosphere. By having the vent passage 49 thus located centrally of and at the uppermost end of the oil reservoir within the piston, a most effective venting of the lash adjuster is obtained. The explanation of this is believed to be that the oil-entrained air within the piston tends to concentrate as a vortex around the longitu# dinal axis thereof by reason of the centrifuging effect produced by the rotation of the lash adiuster in operation while the air, being lighter than the oil, tends also to rise therein toward the vent passage dg, the now of excess oil from the reservoir in the same direction insures against the lower end of the air vortex interfering'with the supply of air-free oil to thevalved passage 29. The continuous communication, which the depression 5U and grooves 57| in the end face of the push rod provide, between the upper end of the vent passage 49 and the atmosphere above the lash adjuster permits this flow of oil in the manner described.

We claim:

In an internal combustion engine valve operating mechanism, a cam, a hydraulic lash adjuster mounted for reciprocation and axial rotation by the cam, and a push rod for transmitting reciprocating movements of the lash adjuster to the valve, said lash adjuster having a hollow piston with a removable plug in one end forming an abutment for the push rod, said plug being centrally apertured end-wise of the piston and said push rod having its plug abutting surface relieved by a transverse groove connecting said aperture to atmosphere.

2. In combination with a cam for operating a poppet valve, an upright cup shaped cylinder arranged for axial rotation and reciprocation by the cam, an upright cup-shaped piston within and slidably supported by the cylinder, and a push rod between the piston and the valve, said piston having an opening in its bottom end `for passage of fluid from within the piston, said cylinder and piston having communicating side ports above said opening for admitting uid under pressure into the piston, a plug substantially closing the upper end of the piston and forming a socket for the lower end of the push rod, said plug having an aperture terminating in said socket for conducting excess fluid and entrained air from the interior of the piston to said socket, said push rod having its lower end relieved by a groove extending from said aperture to exterior of the socket for conducting said excess fluid and entrained air out of said socket.

3. In an internal combustion engine valve operating mechanism including two telescoping cup shaped members having a body of fluid in thrust transmitting relation therebetween, means for supplying fluid to said body including a reservoir in the inner cup shaped member, a source of fluid external to the outer cup-shaped member, said inner and outer cup-shaped members having communicating passages connecting said reservoir and said external fluid source a plug on the end of the inner member farthest from said body having a central passage therethrough, a valve engaged member in abutment with said plug circumferentially of said passage having a groove in its plug abutting surface for conducting iiuid from said passage to the atmosphere.

4. In combination with a cam and a push rod for operating a valve, an upright cup shaped cylinder arranged for axial rotation and reciprocation by the cam, a cup shaped piston slidably supported by and in nesting relation with the cylinder, means for introducing fluid to the interior of the piston for subsequent delivery to the cylinder below the piston, a plug substantially closing the upper end of the piston and forming an abutment thereon for the push rod, said plug having a passage aligned with the axis of rotation of the cylinder through which excess fluid and entrained air supplied to the piston may pass, and cooperating grooves on the plug opposed end of the push rod for conducting said excess fluid and entrained air to atmosphere from the upper end of said passage.

5. A push rod for transmitting thrust between a hydraulic lash adjuster and a rocker in a poppet valve operating mechanism having an external generally spherical thrust face adapted to socket in one end of the lash adjuster, said thrust face having an external groove extending outwardly from the center thereof to one side of the push rod for the passage of excess iluid and entrained gases conducted to said socket from within the lash adjuster.

6. A push rod for transmitting thrust between a hydraulic lash adjuster and a rocker in a poppet valve operating mechanism having an end portion terminating in a central depression, a generally spherical external surface bordering said depression adapted to seat in a spherical socket of the lash adjuster, said surface terminating at vthe side edges of said end portion and having an external groove interconnecting said side edges and said depression for venting said depression to atmosphere when the push rod is in thrust transmitting relation with the lash adjuster.

7. In an internal combustion engine valve operating mechanism, a cam, a hydraulic lash ad- `V6 juster mounted for reciprocation and axial rotation by the cam, and a push rod for transmitting reciprocating movements of the lash adjuster to the valve, said lash adjuster cornprising a cylinder closed at one end, a body of hydraulic fluid in the closed end of the cylinder and a hollow cup-shaped piston resting on said body, means in the bottom of said piston for introducing fluid to said body from the interior of the piston, a source of iluid under pressure externally of the lash adjuster cylinder, said cylinder and piston having communicating side ports through which fluid from said source is delivered in excess of requirements to the interior of the piston, a member interposed between the push rod and the piston and forming a closure for the push rod end of the piston, said member having an air and excess fluid escape passage extending therethrough in line with the axis of rotation of the lash adjuster, said push rod having a groove in its end face opposite said member connecting said passage to atmosphere.

8. In combination, a pair of slidably nested cup-shaped members forming a fluid pressure chamber between their bottom walls, a :uid reservoir within the inner member, said inner member having a one-way valved passage through which fluid may enter the pressure chamber from said reservoir, an external source of fluid under pressure, said members having communicating side ports connecting said reservoir to said source, and a member capping said inner member to conne uid therein, said capping member having a vertical passage extending centrally therethrough and open at its lower end to said reservoir, a spherically concave seat on said capping member surrounding the upper end of said passage, and a rod having a spherical end socketed in said seat, said spherical end having a downwardly presenting relief groove connecting the upper end of said passage to the atmosphere exteriorly of said push rod and members.

9. In a reciprocating hydraulic lash adjuster and push rod assembly in which high rotating speeds are imparted to the lash adjuster during rotation, said lash adjuster having a cylinder, a body of fluid, and a hollow piston in series thrust transmitting relation with each other, means for supplying fluid to said body including a second body of iluid within the piston and a one-way valved passage interconnecting said bodies, said piston and cylinder having conimunicating side ports for supplying fluid to replenish said second body, said piston and push rod having a ball and socket abutment on the axis of rotation of the lash adjuster, and means for centrally venting the interior of the piston at its push rod end, said means including a central aperture extending through the push rod end of the piston and a connecting groove extending transversely across the piston end of the push rod.

10. In combination, a rotatively and recipro- Catively driven hydraulic lash adjuster including an upright cup-shaped piston in one end forming a reservoir for receiving aerated hydraulic uid during rotation and reciprocation, said piston having a plug in its upper end forming the upper end of said reservoir, said plug having a passage extending therethrough coaxial with the axis of rotation of the piston and an upwardly presenting concave seating surface surrounding the upper terminus of said passage, a source of aerated hydraulic fluid externally of the lash References Cited in the le of this patent Number UNITED STATES PATENTS Name Date Hallett Mar. 31, 1931 Burkhardt July 4, 1933 Voorhies Apr. 8, 1941 

